In the game itself, players purchase packs of cards with in-game money. These packs contain random players and other items, such as balls and kits, and players have to win football matches in order to earn coins, to purchase new players. There are other ways to make money, such as buying players cheaply and selling them on for a higher price.

It lets users create their own teams by buying, selling, trading, and auctioning off their players with thousands of other users. Gamers earn points by playing their teams online or offline

copied from Fifa 09 and Fifa 11 Wiki articles, i hope it helped.